Dennis,
I have been down this path many times. Call them what you will, pimples, acne, spots, who cares what they're called you don't want red spots on your face. Some "experts" will tell you they have nothing to do with diet and others will tell you they do. Here is what I have found thru trial and error over almost 30 (yes I'm 42 and still have problems but not to the extent of when I was a teen).
Foods to avoid: malt and malt products (like milo drinks, malteasers, chocolate malt confectionary), ice cream, whey based protein supplements. These 3 things I have found to be the "kings of zits". In small quantities these are OK but any more than 2 serves a day and within 2 days I'll be paying for the indulgence. Chocolate to a lesser degree but i find these days that I can eat a lot (ie most of a large block) before I get any problems.
So, I now have to use either egg or soy based protein supplements and these don't cause me any troubles.
One more thing I've found that works is try using your girlfriends/wifes/sisters/mums skin care products. Sounds girly but if you use these instead of soap to wash your face you will find that over time the amount of oil produced by your skin decreases hence reducing the number of pores that become blocked. The more you scrub every last bit of oil away, the more this tells your skin to produce more oil. Anyway, this is what i've found.
Hope this helps.